MySQl基本查询

淡淡的烟草味﹌ 2021-07-24 20:48 399阅读 0赞

**一 数据准备**

首先定义数据表，输入语句如下。

CREATE TABLE fruits
    (
        f_id    char(10)         NOT NULL,
        s_id    INT            NOT NULL,
        f_name  char(255)      NOT NULL,
        f_price decimal(8,2)      NOT NULL,
        PRIMARY KEY(f_id)
    );

插入如下数据：

INSERT INTO fruits (f_id, s_id, f_name, f_price)
         VALUES('a1', 101,'apple',5.2),
         ('b1',101,'blackberry', 10.2),
         ('bs1',102,'orange', 11.2),
         ('bs2',105,'melon',8.2),
         ('t1',102,'banana', 10.3),
         ('t2',102,'grape', 5.3),
         ('o2',103,'coconut', 9.2),
         ('c0',101,'cherry', 3.2),
         ('a2',103, 'apricot',2.2),
         ('l2',104,'lemon', 6.4),
         ('b2',104,'berry', 7.6),
         ('m1',106,'mango', 15.6),
         ('m2',105,'xbabay', 2.6),
         ('t4',107,'xbababa', 3.6),
         ('m3',105,'xxtt', 11.6),
         ('b5',107,'xxxx', 3.6);

使用SELECT语句查询f\_id字段的数据。

mysql> SELECT f_id, f_name FROM fruits;
    +------+------------+
    | f_id | f_name     |
    +------+------------+
    | a1   | apple      |
    | a2   | apricot    |
    | b1   | blackberry |
    | b2   | berry      |
    | b5   | xxxx       |
    | bs1  | orange     |
    | bs2  | melon      |
    | c0   | cherry     |
    | l2   | lemon      |
    | m1   | mango      |
    | m2   | xbabay     |
    | m3   | xxtt       |
    | o2   | coconut    |
    | t1   | banana     |
    | t2   | grape      |
    | t4   | xbababa    |
    +------+------------+
    16 rows in set (0.02 sec)

**二 表单查询**

1 从fruits表中检索所有字段的数据。

mysql> SELECT * FROM fruits;
    +------+------+------------+---------+
    | f_id | s_id | f_name     | f_price |
    +------+------+------------+---------+
    | a1   |  101 | apple      |    5.20 |
    | a2   |  103 | apricot    |    2.20 |
    | b1   |  101 | blackberry |   10.20 |
    | b2   |  104 | berry      |    7.60 |
    | b5   |  107 | xxxx       |    3.60 |
    | bs1  |  102 | orange     |   11.20 |
    | bs2  |  105 | melon      |    8.20 |
    | c0   |  101 | cherry     |    3.20 |
    | l2   |  104 | lemon      |    6.40 |
    | m1   |  106 | mango      |   15.60 |
    | m2   |  105 | xbabay     |    2.60 |
    | m3   |  105 | xxtt       |   11.60 |
    | o2   |  103 | coconut    |    9.20 |
    | t1   |  102 | banana     |   10.30 |
    | t2   |  102 | grape      |    5.30 |
    | t4   |  107 | xbababa    |    3.60 |
    +------+------+------------+---------+
    16 rows in set (0.00 sec)

2 查询fruits表中f\_name列所有水果名称。

3 从fruits表中获取f\_name和f\_price两列

该语句使用SELECT声明从fruits表中获取名称为f\_name和f\_price两个字段下的所有水果名称和价格，两个字段之间用逗号分隔开。

select f_name,f_price from fruits
    +------------+---------+
    | f_name     | f_price |
    +------------+---------+
    | apple      |    5.20 |
    | apricot    |    2.20 |
    | blackberry |   10.20 |
    | berry      |    7.60 |
    | xxxx       |    3.60 |
    | orange     |   11.20 |
    | melon      |    8.20 |
    | cherry     |    3.20 |
    | lemon      |    6.40 |
    | mango      |   15.60 |
    | xbabay     |    2.60 |
    | xxtt       |   11.60 |
    | coconut    |    9.20 |
    | banana     |   10.30 |
    | grape      |    5.30 |
    | xbababa    |    3.60 |
    +------------+---------+
    16 rows in set (0.00 sec)

4 查询价格为10.2元的水果的名称。

5 查找名称为“apple”的水果的价格。

6 查询价格小于10的水果的名称。

SELECT f_name, f_price
    FROM fruits
    WHERE f_price < 10;
    +---------+---------+
    | f_name  | f_price |
    +---------+---------+
    | apple   |    5.20 |
    | apricot |    2.20 |
    | berry   |    7.60 |
    | xxxx    |    3.60 |
    | melon   |    8.20 |
    | cherry  |    3.20 |
    | lemon   |    6.40 |
    | xbabay  |    2.60 |
    | coconut |    9.20 |
    | grape   |    5.30 |
    | xbababa |    3.60 |
    +---------+---------+
    11 rows in set (0.01 sec)

7 s\_id为101和102的记录。

SELECT s_id,f_name, f_price
    FROM fruits
    WHERE s_id IN (101,102)
    ORDER BY f_name;
    +------+------------+---------+
    | s_id | f_name     | f_price |
    +------+------------+---------+
    |  101 | apple      |    5.20 |
    |  102 | banana     |   10.30 |
    |  101 | blackberry |   10.20 |
    |  101 | cherry     |    3.20 |
    |  102 | grape      |    5.30 |
    |  102 | orange     |   11.20 |
    +------+------------+---------+
    6 rows in set (0.00 sec)

8 查询所有s\_id不等于101也不等于102的记录。

SELECT s_id,f_name, f_price
    FROM fruits
    WHERE s_id NOT IN (101,102)
    ORDER BY f_name;
    +------+---------+---------+
    | s_id | f_name  | f_price |
    +------+---------+---------+
    |  103 | apricot |    2.20 |
    |  104 | berry   |    7.60 |
    |  103 | coconut |    9.20 |
    |  104 | lemon   |    6.40 |
    |  106 | mango   |   15.60 |
    |  105 | melon   |    8.20 |
    |  107 | xbababa |    3.60 |
    |  105 | xbabay  |    2.60 |
    |  105 | xxtt    |   11.60 |
    |  107 | xxxx    |    3.60 |
    +------+---------+---------+
    10 rows in set (0.00 sec)

9 查询价格在2.00元到10.20元之间的水果名称和价格。

mysql> SELECT f_name, f_price FROM fruits WHERE f_price BETWEEN 2.00 AND 10.20;
    +------------+---------+
    | f_name     | f_price |
    +------------+---------+
    | apple      |    5.20 |
    | apricot    |    2.20 |
    | blackberry |   10.20 |
    | berry      |    7.60 |
    | xxxx       |    3.60 |
    | melon      |    8.20 |
    | cherry     |    3.20 |
    | lemon      |    6.40 |
    | xbabay     |    2.60 |
    | coconut    |    9.20 |
    | grape      |    5.30 |
    | xbababa    |    3.60 |
    +------------+---------+
    12 rows in set (0.00 sec)

10 查询价格在2.00元到10.20元之外的水果名称和价格。

11 查找所有以'b'字母开头的水果。

SELECT f_id, f_name
    FROM fruits
    WHERE f_name LIKE 'b%';
    +------+------------+
    | f_id | f_name     |
    +------+------------+
    | b1   | blackberry |
    | b2   | berry      |
    | t1   | banana     |
    +------+------------+
    3 rows in set (0.00 sec)

12 在fruits表中，查询f\_name中包含字母'g'的记录。

SELECT f_id, f_name
    FROM fruits
    WHERE f_name LIKE '%g%';
    +------+--------+
    | f_id | f_name |
    +------+--------+
    | bs1  | orange |
    | m1   | mango  |
    | t2   | grape  |
    +------+--------+
    3 rows in set (0.00 sec)

13 查询以''b开头，并以'y'结尾的水果的名称。

SELECT f_name
    FROM fruits
    WHERE f_name LIKE 'b%y';
    mysql> SELECT f_id, f_name
        -> FROM fruits
        -> WHERE f_name LIKE '%g%';
    +------+--------+
    | f_id | f_name |
    +------+--------+
    | bs1  | orange |
    | m1   | mango  |
    | t2   | grape  |
    +------+--------+
    3 rows in set (0.00 sec)

14 在fruits表中，查询以字母'y'结尾，且'y'前面只有4个字母的记录。

mysql> SELECT f_id, f_name FROM fruits WHERE f_name LIKE '____y';
    +------+--------+
    | f_id | f_name |
    +------+--------+
    | b2   | berry  |
    +------+--------+
    1 row in set (0.00 sec)

**三 条件查询**

在数据库中创建数据表customers，该表中包含了本章中需要用到的数据。

CREATE TABLE customers
    (
      c_id      int       NOT NULL AUTO_INCREMENT,
      c_name    char(50)  NOT NULL,
      c_address char(50)  NULL,
      c_city    char(50)  NULL,
      c_zip     char(10)  NULL,
      c_contact char(50)  NULL,
      c_email   char(255) NULL,
      PRIMARY KEY (c_id)
    );

为了演示需要插入数据，插入执行以下语句。

INSERT INTO customers(c_id, c_name, c_address, c_city,
    c_zip,  c_contact, c_email)
    VALUES(10001, 'RedHook', '200 Street ', 'Tianjin',
    '300000',  'LiMing', 'LMing@163.com'),
    (10002, 'Stars', '333 Fromage Lane',
    'Dalian', '116000',  'Zhangbo','Jerry@hotmail.com'),
    (10003, 'Netbhood', '1 Sunny Place', 'Qingdao',  '266000',
    'LuoCong', NULL),
    (10004, 'JOTO', '829 Riverside Drive', 'Haikou',
    '570000',  'YangShan', 'sam@hotmail.com');
    mysql> SELECT COUNT(*) AS cust_num  FROM customers;
    +----------+
    | cust_num |
    +----------+
    |        4 |
    +----------+
    1 row in set (0.01 sec)

15 查询customers表中c\_email为空的记录的c\_id、c\_name和c\_email字段值。

16 查询customers表中c\_email不为空的记录的c\_id、c\_name和c\_email字段值。

17 在fruits表中查询s\_id = 101，并且f\_price大于等于5的水果价格和名称。

mysql> SELECT f_id, f_price, f_name FROM fruits WHERE s_id = '101' AND f_price >=5;
    +------+---------+------------+
    | f_id | f_price | f_name     |
    +------+---------+------------+
    | a1   |    5.20 | apple      |
    | b1   |   10.20 | blackberry |
    +------+---------+------------+
    2 rows in set (0.00 sec)

18 在fruits表中查询s\_id = 101或者102，且f\_price大于5，并且f\_name=‘apple’的水果价格和名称。

mysql> SELECT f_id, f_price, f_name FROM fruits WHERE s_id IN('101', '102') AND f_price >= 5 AND f_name = 'apple';
    +------+---------+--------+
    | f_id | f_price | f_name |
    +------+---------+--------+
    | a1   |    5.20 | apple  |
    +------+---------+--------+
    1 row in set (0.00 sec)

19 查询s\_id=101或者s\_id=102的水果供应商的f\_price和f\_name。

mysql> SELECT s_id,f_name, f_price FROM fruits WHERE s_id = 101 OR s_id = 102;
    +------+------------+---------+
    | s_id | f_name     | f_price |
    +------+------------+---------+
    |  101 | apple      |    5.20 |
    |  101 | blackberry |   10.20 |
    |  102 | orange     |   11.20 |
    |  101 | cherry     |    3.20 |
    |  102 | banana     |   10.30 |
    |  102 | grape      |    5.30 |
    +------+------------+---------+
    6 rows in set (0.00 sec)

20 查询s\_id=101或者s\_id=102的水果供应商的f\_price和f\_name。

mysql> SELECT s_id,f_name, f_price FROM fruits WHERE s_id IN(101,102);
    +------+------------+---------+
    | s_id | f_name     | f_price |
    +------+------------+---------+
    |  101 | apple      |    5.20 |
    |  101 | blackberry |   10.20 |
    |  102 | orange     |   11.20 |
    |  101 | cherry     |    3.20 |
    |  102 | banana     |   10.30 |
    |  102 | grape      |    5.30 |
    +------+------------+---------+
    6 rows in set (0.00 sec)

21 查询fruits表中s\_id字段的值，返回s\_id字段值且不得重复。

mysql> SELECT DISTINCT s_id FROM fruits;
    +------+
    | s_id |
    +------+
    |  101 |
    |  103 |
    |  104 |
    |  107 |
    |  102 |
    |  105 |
    |  106 |
    +------+
    7 rows in set (0.00 sec)

22 查询fruits表的f\_name字段值，并对其进行排序。

23 查询fruits表中的f\_name和f\_price字段，先按f\_name排序，再按f\_price排序。

mysql> SELECT f_name, f_price FROM fruits ORDER BY f_name, f_price;
    +------------+---------+
    | f_name     | f_price |
    +------------+---------+
    | apple      |    5.20 |
    | apricot    |    2.20 |
    | banana     |   10.30 |
    | berry      |    7.60 |
    | blackberry |   10.20 |
    | cherry     |    3.20 |
    | coconut    |    9.20 |
    | grape      |    5.30 |
    | lemon      |    6.40 |
    | mango      |   15.60 |
    | melon      |    8.20 |
    | orange     |   11.20 |
    | xbababa    |    3.60 |
    | xbabay     |    2.60 |
    | xxtt       |   11.60 |
    | xxxx       |    3.60 |
    +------------+---------+
    16 rows in set (0.00 sec)

24 查询fruits表中的f\_name和f\_price字段，对结果按f\_price降序方式排序。

mysql> SELECT f_name, f_price FROM fruits ORDER BY f_price DESC;
    +------------+---------+
    | f_name     | f_price |
    +------------+---------+
    | mango      |   15.60 |
    | xxtt       |   11.60 |
    | orange     |   11.20 |
    | banana     |   10.30 |
    | blackberry |   10.20 |
    | coconut    |    9.20 |
    | melon      |    8.20 |
    | berry      |    7.60 |
    | lemon      |    6.40 |
    | grape      |    5.30 |
    | apple      |    5.20 |
    | xxxx       |    3.60 |
    | xbababa    |    3.60 |
    | cherry     |    3.20 |
    | xbabay     |    2.60 |
    | apricot    |    2.20 |
    +------------+---------+
    16 rows in set (0.00 sec)

25 查询fruits表，先按f\_price降序排序，再按f\_name字段升序排序。

mysql> SELECT f_price, f_name FROM fruits ORDER BY f_price DESC, f_name;
    +---------+------------+
    | f_price | f_name     |
    +---------+------------+
    |   15.60 | mango      |
    |   11.60 | xxtt       |
    |   11.20 | orange     |
    |   10.30 | banana     |
    |   10.20 | blackberry |
    |    9.20 | coconut    |
    |    8.20 | melon      |
    |    7.60 | berry      |
    |    6.40 | lemon      |
    |    5.30 | grape      |
    |    5.20 | apple      |
    |    3.60 | xbababa    |
    |    3.60 | xxxx       |
    |    3.20 | cherry     |
    |    2.60 | xbabay     |
    |    2.20 | apricot    |
    +---------+------------+
    16 rows in set (0.00 sec)

26 根据s\_id对fruits表中的数据进行分组。

mysql> SELECT s_id, COUNT(*) AS Total FROM fruits GROUP BY s_id;
    +------+-------+
    | s_id | Total |
    +------+-------+
    |  101 |     3 |
    |  102 |     3 |
    |  103 |     2 |
    |  104 |     2 |
    |  105 |     3 |
    |  106 |     1 |
    |  107 |     2 |
    +------+-------+
    7 rows in set (0.00 sec)

27 根据s\_id对fruits表中的数据进行分组，将每个供应商的水果名称显示出来。

mysql> SELECT s_id, GROUP_CONCAT(f_name) AS Names FROM fruits GROUP BY s_id;
    +------+-------------------------+
    | s_id | Names                   |
    +------+-------------------------+
    |  101 | apple,blackberry,cherry |
    |  102 | orange,banana,grape     |
    |  103 | apricot,coconut         |
    |  104 | berry,lemon             |
    |  105 | melon,xbabay,xxtt       |
    |  106 | mango                   |
    |  107 | xxxx,xbababa            |
    +------+-------------------------+
    7 rows in set (0.00 sec)

28 根据s\_id对fruits表中的数据进行分组，并显示水果种类大于1的分组信息。

mysql> SELECT s_id, GROUP_CONCAT(f_name) AS Names FROM fruits GROUP BY s_id HAVING COUNT(f_name) > 1;
    +------+-------------------------+
    | s_id | Names                   |
    +------+-------------------------+
    |  101 | apple,blackberry,cherry |
    |  102 | orange,banana,grape     |
    |  103 | apricot,coconut         |
    |  104 | berry,lemon             |
    |  105 | melon,xbabay,xxtt       |
    |  107 | xxxx,xbababa            |
    +------+-------------------------+
    6 rows in set (0.00 sec)

29 根据s\_id对fruits表中的数据进行分组，并显示记录数量。

mysql> SELECT s_id, COUNT(*) AS Total FROM fruits GROUP BY s_id WITH ROLLUP;
    +------+-------+
    | s_id | Total |
    +------+-------+
    |  101 |     3 |
    |  102 |     3 |
    |  103 |     2 |
    |  104 |     2 |
    |  105 |     3 |
    |  106 |     1 |
    |  107 |     2 |
    | NULL |    16 |
    +------+-------+
    8 rows in set (0.00 sec)

为了演示效果，首先创建数据表。

CREATE TABLE orderitems
    (
      o_num      int          NOT NULL,
      o_item     int          NOT NULL,
      f_id       char(10)     NOT NULL,
      quantity   int          NOT NULL,
      item_price decimal(8,2) NOT NULL,
      PRIMARY KEY (o_num,o_item)
    ) ;

然后插入演示数据。

INSERT INTO orderitems(o_num, o_item, f_id, quantity, item_price)
    VALUES(30001, 1, 'a1', 10, 5.2),
    (30001, 2, 'b2', 3, 7.6),
    (30001, 3, 'bs1', 5, 11.2),
    (30001, 4, 'bs2', 15, 9.2),
    (30002, 1, 'b3', 2, 20.0),
    (30003, 1, 'c0', 100, 10),
    (30004, 1, 'o2', 50, 2.50),
    (30005, 1, 'c0', 5, 10),
    (30005, 2, 'b1', 10, 8.99),
    (30005, 3, 'a2', 10, 2.2),
    (30005, 4, 'm1', 5, 14.99);

30 查询订单价格大于100的订单号和总订单价格。

返回的结果中orderTotal列的总订单价格并没有按照一定顺序显示，接下来，使用ORDER BY关键字按总订单价格排序显示结果。

mysql> SELECT o_num,  SUM(quantity * item_price) AS orderTotal FROM orderitems GROUP BY o_num HAVING SUM(quantity*item_price) >= 100;
    +-------+------------+
    | o_num | orderTotal |
    +-------+------------+
    | 30001 |     268.80 |
    | 30003 |    1000.00 |
    | 30004 |     125.00 |
    | 30005 |     236.85 |
    +-------+------------+
    4 rows in set (0.02 sec)

31 显示fruits表查询结果的前4行。

mysql> SELECT * From fruits LIMIT 4;
    +------+------+------------+---------+
    | f_id | s_id | f_name     | f_price |
    +------+------+------------+---------+
    | a1   |  101 | apple      |    5.20 |
    | a2   |  103 | apricot    |    2.20 |
    | b1   |  101 | blackberry |   10.20 |
    | b2   |  104 | berry      |    7.60 |
    +------+------+------------+---------+
    4 rows in set (0.00 sec)

32 在fruits表中，使用LIMIT子句，返回从第5个记录开始的，行数长度为3的记录。

mysql> SELECT * From fruits LIMIT 4, 3;
    +------+------+--------+---------+
    | f_id | s_id | f_name | f_price |
    +------+------+--------+---------+
    | b5   |  107 | xxxx   |    3.60 |
    | bs1  |  102 | orange |   11.20 |
    | bs2  |  105 | melon  |    8.20 |
    +------+------+--------+---------+
    3 rows in set (0.00 sec)